Photographic-printing paper and process of making the same



T P. MIDDLETON.

PHOTOGRAPHIC PRINTING PAPER AND-PROCESS OF MAKING THE SAME.

APPLICATION FILED APR. 24. 1919.

l ,329, 9 l 8. Patented Feb. 3, 1920.

UNITED STATES PATENT OFFICE.

THOMAS P. MIDDLETON, OF LONDON, ENGLAND, ASSIG-NOR TO KEROTYPE, LIMITED, OF

LONDON, ENGLAND.

PHOTOGRAPHIG-PRINTING PAPER AND PROCESS OF MAKING THE SAME.

Specification of Letters Patent.

Patented Feb. 3, 1920.

Application filed April 24, 1919. Serial No. 292,514.

Same, of which the following is a specifica- .tion.

The present invention is for improvements in manufacturing photographic transfer character described in the specifications of F. W. Kent and T. P. Middletons United States of America Letters Patent No. 1,299,479, dated. 8th April, 1919, and of F. W. Kents Letters Patent No. 1,228,680, dated 5th June, 1917 these improvements conducing to better industrial manufacture and to an improved "product.

. It has been found to .be desirable to separate the operations of coating the waxed paper base with substratum and coating with emulsion. The following advantages, are thereby secured.

1'. There is no large mass of heated wax at that end of the coating room which it is desirable to keep cool.

2. There are no fumes from the wax and substratum in the closeness of the dark coating room.

,3. It is possible to prepare the base so that it shall be ready for coating by other manufacturers without the aid of special vma- 'chinery.

grains of one resinous constituent standout in grains in a film of the other resinous constituent, the texture of this complex of two species tending against such strains and stresses in the film as may induce toward Thus we have grains of resself stripping.

and a film or filling of a resinous substance mous film.

To producethe required resinous complex, the principle of the well known mat varnish of the photographer is brought into service. Two resinous materials (as sandarac and mastic) are required also two solvents, (as ether and benzene). The action may be by the deposition of one resinous constituent in grains following the evaporation of the more volatile constituent of the mixed solvent: the deposited grains being insoluble in the remaining solvent.

The, sandarac being insoluble in benzene, the grains of sandarac are precipitated by the evaporation of the ether, whereas mastic is freely soluble and remains as a varnish.

The use of two resinous contituents does not necessarily. involve the use of two commercial resins as certain commercial resins which are available for the purposes of this invention contain two constituents. It is,

- however, generally preferred to control the 'nal su stratum should be a solution or nearly complete solution, as the powder thereby obtained is much finer in the grain and more even than if held merely in suspension,

The solvent must contain two or more components one vent for wax and the other of which should have little or no solvent action; but the former must not be too free a solvent.

In addition the wax solvent component must be the more volatile of the two. The Wax non-solvent component may be a water soluble alcohol, 6. 9., ethyl or methyl alcohol or a mixture of these and the wax solvent component may consist of di-methyl, methylethyl or acetic ethers or their homologues.

In general, such a substratum will contain two solids, both soluble or almost soluble in the mixture of liquids, but one insolulole or nearly so in one of the solvents; so that as drying takes place, a resin is precipitated while another dries as a varnish. Water will often be found to facilitate this action as some bodies which are soluble in alcohol are not soluble to the same extent in 90% alcohol.

Occasionally, the substratum-will appear to only contain one solid, as in the case of elemi, one form of which though completely soluble in'ether-alcohol is only parof which must be a good sol-- action on a. sensitive emulsion.

may be coarser as the paper is smoother and vice versa. In addition, the total amount of solids in the substratum should be no more than is required to secure proper adhesion.

The proportion of solvents present will also have some influence on the grain but in general these solventswill be chosen to suit "the conditions of waxing; and these conditions are dependent upon the nature and porosity of the aper, the temperature at which waxing ta es place and the time the paper remains in the wax. One of the great advantages of this invention is that these conditions are now rendered independent of the coating running speed; and so wider variation is possible in the nature and thickness of the paper; and if necessary the temperature of the waxcan .be near the boiling (or dissociation) pointand the time much prolonged; so that very perfect waxing is possible. The ease with which stripping takes place partly depends on the solve ts used and the proportions in which the sblvents are present; and such a mixture must self or automatic stripping. The more =minute.

be selected as will ive good facilities for stripping while avoiding any tendency to perfect the waxing the greater must be the affinity of the solvent for the wax. v

Care must always'be taken that no impurity is present in the solvents which,'if left on evaporation, would have a deleterious effect on the subsequent emulsion coatmg.

Methylated ether 720. Sp. Gm" 3 ounces. Methylated alcohol 90% 3 g In this exam le the paper base used was a plain paper prepared for photographic purposes weighing 90 grams per square meter; the temperature of waxing being 250 F. and the running speed 12 feet per This gave a very satisfactory product; with easy stripping and no tendency to The following are examples of possible" ing.

automatic or self stripping when the emulslon coating was thin.

B. In another example, where a thinner ,plain paper not prepared for photographic purposes and of very inferior quality was used, being that in use for lining shelves, etc., weightabout 75 grams per square meter; temperature of waxing about 220 F. and running speed 10 feet per minute, the waxing being more perfect than in the previous example, the following was used and gave results comparable to example A..

Sandarac 90 grains. Mastic 20 Alcohol 90% 4% ounces. Acetic ether (anhyd.) 1T} In this example B the substitution of acetic ether for methylated ether, the former havlng a greater affinity for the wax, enables perfect adhesion to be realized notwith'-,

standing the more complete waxing of the paper.

The formula in example B is one which will also serve for the conditions of waxing and class of paper set forth in relation to the formula in example A if the emulsion coating is to be thick and the amount of- 2. On the presence or absence of hygroscop ic bodies either added intentionally, e. 9., glycerin, or unintentionally,'e. 9., nitrates left by imperfect washing.

3. On the nature of the original gelatin, i. 6., whether hard or soft and on the amount of chrome or other alum added (if any).

Whether the substratuming and coating operations are carried out separately, as in general is preferred, or are carried out as a continuous operation as may in some cases be required, some departures .from the machine described in the'filater of the hereinabove mentioned specifications are advisable in view of the more volatile nature of the substratum according to the present invention, this increased volatility tending toward undesirable clogging and consequent, unevenness 1n the coating and trouble in dry- To avoid these difficulties and in general to promote easy manufacture, the machine illustrated diagrammatically in the accompanying drawings will serve.

Referring to the drawings a designates an electrically heated waxing dish in which. paraffin wax is kept at a temperature of about 250 F. A parafiin wax having a melting point of 132134 F. will serve. The paper b from a supply roller 0 is led back and forth more than once through the wax. On leaving the wax the paper passes between doctors or rollers d, d for removing excess of wax. Thence the paper passes upward to be buffed or polished by passing between a roller 6 and a polishing buff or brush f which revolves at a speed much higher than the surface speed of the paper, a working example being: peripheral speed of the buff 1500 to 2000 feet per minute; surface speed of the paper 10 to 12 feet per minute. After bufling the paper passes to a substratuming dish 9 and then through a horizontal drying trunk or chamber h. This trunk 12. is heated as for example with a hot water coil iand air is exhausted therefrom by means of a fan or the like thus preventing the fumes going out in the room.

The substratum is applied by means of two rollers j, j in contact, roller j dipping in the coating trough and running anticlockwise and in contrary sense to the other roller j, and the superfluous substratum being if necessary removed by means of a wiper is which may consist of two thickmesses-of flannel folded around a lath. Load Z gives the necessary pressure.

All the paper-web bending rollers are driven at the surface running speed. On leaving the drying chamber the paper passes to an ordinary rewinding machlne if the substratuming and coating operations are to be carried out separately, otherwise as a continuous operation, the paper b goes to an emulsion coating device m of ordinary type and after coating, is carried through a cooling chamber a by means of endless tapes 0 running at a speed considerably faster than the surface running speed. Cold air may be blown into the chamber in this case.

()n emerging from this chamber the paper 1) passes to a suitable looping machine for drying.

What I claim is 1. Process of making photographic printing and transfer paper which comprises satmating with wax a sheet of paper, and coating the paper with a mat resinous complex,

comprising two constituents delivered from mixed solvents, as a substratum to a sensitive stratum, substantially as described.

2. Process of making photographic printing and transfer paper which comprises saturating with wax a sheet of paper, and coating the paper with a solution of mixed solvents of a resinous complex giving on drying as a substratum to a sensitive stratum a film in which grains of one resinous constituent stand out in grains in a film of another resinous constituent, substantially as described.

3. Photographic printing and transfer paper comprising a base of wax saturated paper on which is a substratum consisting of a mat resinous complex comprising two constituents delivered from mixed solvents, substantially as described.

4:. As the support for the sensitive stra tum of photographic printing and transfer paper of the general character referred to, a base of wax saturated paper carrying a substratum consisting of a mat resinous complex comprising two constituents delivered from mixed solvents.

5. The herein described process of preparing photographic printing and transfer paper which comprises conducting paper in the web through melted paraffin wax, thence between rollers to a buffing device, thence to a substratum coating device which applies and distributes the substratuming solution, also removes the excess, and thence throu h a chamber arranged so as to keep the su stratum coating device free from any disturbing effect from the evaporation taking place in the drying chamber.

In testimony whereof I affix my signature.

THOS. P. MIDDLETON. 

